Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-02-01
2002-07-30
Truong, Duc (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S401000, C525S402000, C528S245000, C528S246000, C528S249000
Reexamination Certificate
active
06426393
ABSTRACT:
FIELD OF THE INVENTION
The present invention concerns a polyacetal copolymer which is excellent in thermal stability and also has shock resistance, rigidity and creep resistant property, and a method of manufacturing the same.
PRIOR ART
Since polyacetal resins are excellent in the balance for mechanical properties, chemical resistance, sliding property, etc. and easy to be fabricated, they are generally utilized, as typical engineering plastics mainly for electric and electronic parts, automobile parts and various other mechanical parts.
However, along with extending application ranges thereof in recent years, higher characteristics have tended to be demanded gradually. For instance, when polyacetal resins are used in thin-walled parts, they often require shock resistance, rigidity and creep resistant property in addition to high flowability and moldability.
However, it is very difficult to improve the properties such as shock resistance, rigidity and creep resistant property together with high flowability and moldability by the modification of a polyacetal resin to the polymer per se.
For example, a method of lowering the degree of polymerization of the polyacetal polymer for the improvement of the flowability and moldability often deteriorates properties such as shock resistance, rigidity and creep resistant property. On the other hand, even if the polymerization degree of the polyacetal polymer is increased, improvement for the shock resistance, rigidity and creep resistance property remains insufficient and the flowability and moldability are greatly deteriorated.
Further, while the flowability of the resin is improved by elevating the molding temperature, not only the essential properties of the polyacetal polymer do not change at all by this method, but also properties such as shock resistance, rigidity and creep resistance property are rather lowered due to the lowering of the molecular weight by the thermal decomposition of the resin or micro-voids formed in the molding products by gases evolved upon thermal decomposition of the resin.
As described above, it is very difficult to make the shock resistance, rigidity and creep resistant property compatible with the high flowability and moldability by the improvement of the polyacetal polymer per se, for which improvement has been demanded. If such polyacetal polymers are obtainable, compositions and application uses in wide ranges utilizing such properties can be expected.
DISCLOSURE OF THE INVENTION
In view of the foregoing situations, the present invention intends to provide a polyacetal polymer having excellent shock resistance, rigidity and creep resistant property as the essential properties of the polymer and enabling high flowability and excellent moldability during molding by the improvement of the thermal stability, as well as a manufacturing method thereof.
For attaining the foregoing object, the present inventors have made an earnest study and, as a result, accomplished the present invention based on the finding that a branched structure formed to a polymer skeleton of a polyacetal polymer by copolymerization with a mono-functional glycidyl compound and the amount of a chlorine compound contained in the mono-functional glycidyl compound used for copolymerization are a factor which is important for the solution of the subject.
That is, the present invention concerns a method of manufacturing a polyacetal copolymer by copolymerization of (a) 100 parts by weight of trioxane, (b) 0.05 to 20 parts by weight of a cyclic ether compound copolymerizable with trioxane and (c) 0.001 to 10 parts by weight of a mono-functional glycidyl compound, in which the mono-functional glycidyl compound (c) with a chlorine content of 0.3% by weight or less is used, as well as a polyacetal copolymer obtained thereby.
DETAILED DESCRIPTION OF THE INVENTION
As hereunder, the polyacetal copolymer of the present invention will be explained in detail.
First, trioxane (a) which is used in the present invention is a cyclic trimer of formaldehyde. Usually it is prepared by the reaction of an aqueous solution of formaldehyde in the presence of an acidic catalyst and is used after purifying by means of distillation or the like. It is preferred that trioxane used for the polymerization contains as little as possible of impurities such as water, methanol and formic acid.
Next, examples of the cyclic ether compound (b) which is used in the present invention copolymerizable with trioxane (a) include ethylene oxide, propylene oxide, butylene oxide, epichlorohydrin, epibromohydrin, styrene oxide, oxetane, 3,3-bis(chloromethyl)oxetane, tetrahydrofuran, trioxepane, 1,3-dioxolane, ethylene glycol formal, propylene glycol formal, diethylene glycol formal, triethylene glycol formal, 1,4-butanediol formal, 1,5-pentanediol formal and 1,6-hexanediol formal. Among them, ethylene oxide and 1,3-dioxolane are preferred.
In the present invention, the copolymerization amount of the cyclic ether compound (b) is from 0.05 to 20 parts by weight, preferably, 0.1 to 15 parts by weight and, particularly preferably, 0.3 to 10 parts by weight based on 100 parts by weight of trioxane as the ingredient (a). If the cyclic ether compound (b) is insufficient, the polymerizing reaction becomes instable and the thermal stability of the resultant polyacetal copolymer is poor. On the other hand, if the ratio of copolymerization of the cyclic ether compound (b) is excessive, mechanical properties such as strength and rigidity are lowered.
Then, the mono-functional glycidyl compound of the ingredient (c) in the polyacetal copolymer according to the present invention is a collective term for organic compounds having one glycidyl group in the molecule and typical examples thereof include glycidol, glycidyl ether comprising an aliphatic alcohol or an aromatic alcohol or a (poly)alkylene glycol adduct thereof with glycidol, and glycidyl ester comprising an aliphatic carboxylic acid or aromatic carboxylic acid or (poly)alkylene glycol adduct thereof with glycidol. Specific examples are methyl glycidyl ether, ethyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, 2-methyloctyl glycidyl ether, phenyl glycidyl ether, p-tertiary-butylphenyl glycidyl ether, sec-butylphenyl glycidyl ether, n-butylphenyl glycidyl ether, phenylphenol glycidyl ether, cresyl glycidyl ether, dibromocresyl glycidyl ether, glycidyl acetate and glycidyl stearate.
The copolymerization amount of the mono-functional glycidyl compound as the ingredient (c) is from 0.001 to 10 parts by weight, preferably, 0.01 to 10 parts by weight and, particularly preferably, 0.1 to 5 parts by weight based on 100 parts by weight of trioxane as the ingredient (a). If the copolymerization amount of the ingredient (c) is less than the above amount, no improving effect for the shock resistance can be obtained, whereas if it becomes excessive, it result in a problem that mechanical properties such as strength and rigidity are deteriorated.
As the mono-functional glycidyl compound (c), it is preferred to use those having a molecular weight of 100 to 1000. If the molecular weight of the mono-functional glycidyl (C) compound is excessive, the branched chain of the polyacetal copolymer formed by copolymerization is made longer to possibly disturb the crystallinity of the resin to deteriorate the basic properties thereof, or give undesired effects on the shock resistant property aimed in the present invention. On the contrary, if the molecular weight of the ingredient (c) is insufficient, the effect to the shock resistant property aimed in the present invention is extremely reduced.
The present invention has a feature in using the mono-functional glycidyl compound (c) having a chlorine content of 0.3% by weight or less, and this enables to manufacture a polyacetal copolymer having excellent thermal stability and also shock resistant property. The chlorine content is preferably 0.1% by weight or less, particularly preferably, 0.05% by weight or less. There is no particular restriction on the lower limit of the chlorine content and i
Okawa Hidetoshi
Tajima Yoshihisa
Nixon & Vanderhye P.C.
Polyplastics Co. Ltd.
Truong Duc
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